Solar‐fuel formation via photoelectrochemical (PEC) routes using water and CO₂ as feedstock has attracted much attention. Most PEC CO₂ reduction studies have been focused on the development of novel photoactive materials; however, there is still a lack of understanding of the key limiting factors of this process. In this study, the theoretical limits of Solar‐to‐Fuel (STF) efficiencies of single‐ and dual‐junction photo‐absorbing materials are illustrated for single‐step multi‐electron CO₂ reduction into fuels including HCOO⁻, CO, CH₃OH and C₂H₅OH. It is also highlighted that STF efficiency depends on the route of two‐step PEC CO₂ reduction process using CH₃OH as a model fuel. Finally, it is illustrated the beneficial role of alternative strategies such as dual‐junction photo‐absorbing electrodes, externally applied bias and subsequent reactor chambers on the maximum theoretical efficiencies of PEC CO₂ reduction.

中文翻译：

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光电化学二氧化碳还原的理论效率极限：与路线有关的热力学分析。

通过光电化学（PEC）路线以水和CO ₂为原料形成太阳能燃料备受关注。大多数减少PEC CO _2的研究都集中在新型光敏材料的开发上。但是，仍然缺乏对该过程关键限制因素的理解。在这项研究中，单和双结光吸收材料的太阳能-燃料（STF）的效率的理论极限是示出了用于单步多电子CO ₂还原成燃料，包括HCOO ^-，CO，CH ₃ OH和C ₂ H ₅ OH。还需要强调的是，STF效率取决于两步PEC CO ₂的路线CH ₃ OH作为模型燃料的还原过程。最后，说明了替代策略（例如双结光吸收电极，外部施加的偏压和后续的反应室）对PEC CO ₂还原的最大理论效率的有益作用。